Because biological denitrification essentially requires a carbon source that acts as an electron donor, in conventional methods for direct purification of nitrate-polluted groundwater, i.e. groundwater polluted with nitrogen in the form of nitrates, denitrificans and water-soluble carbon sources were charged into groundwater separately. However, in such conventional methods, diffusion of the denitrificans and the water-soluble carbon sources in to the vein occur, and sufficient effect could not be generated.
Further, for the purpose of providing drinking water, the use of toxic carbon sources such as methanol had to be avoided and the carbon source that could be used for denitrification were limited.
Furthermore, since most enzymes involved in the denitrification metabolism are metal enzymes, the addition of a small amount of heavy metals such as Fe, Mo, Mn or Cu has been considered necessary for the denitrificans to sustain high activity. However, there is a problem in that the metal content of groundwater varies and water with high metal content is not suitable for drinking.
Hence, the object of the present invention is to overcome the above-described problems of the prior art and to provide a novel safe purification method that enables the efficient use of carbon sources and the concentration of denitrificans, and does not require the addition of heavy metals, as well as an apparatus for such method.